Theoretical corrections for dynamical scattering (multiple scattering) will be developed and applied to problems of biological structure, with the objective of obtaining quantitative interpretations of electron diffraction intensities. The usefulness of an approximation derived by Schiff for small angle scattering will be tested by incorporating the equation in a crystallographic structure- factor program. Experimental electron diffraction intensities will be compared to calculated intensities for the known structure of glycine in order to determine whether a crystallographically acceptable reliability factor can be obtained. Other, more conventional multiple-slice methods will also be used. Experimental data will be obtained at voltages up to 650 kV as well as at the conventional voltage of 80 kV. On the basis of experience gained by working with the known structure of crystalline glycine, methods will be developed for dynamical scattering corrections in the interpretation of image intensities. Investigation of virus particles and similarly sized structures by either Fourier transformation of electron microscope images or by equivalent projection matrix methods will be put on a sounder theoretical basis as a consequence of accounting in a proper way for the effects of dynamical scattering.